1. Field of the Invention
The present invention relates generally to a method of manufacturing metal titanate fine powder and more particularly is directed to a method of manufacturing barium titanate, strontium titanate and calcium titanate fine powder by liquid-phase reaction.
2. Description of the Prior Art
Recently, manufacturing of metal titanate ultra-fine powder such as barium titanate BaTiO.sub.3, strontium titanate SrTi0.sub.3 and calcium titanate CaTiO.sub.3 ultra-fine powders has been requested from various points of view. One of such requirements relates to a multilayer ceramic condenser. The condenser is required to be small-sized and light-weighted similarly to other electronic parts. In the aspect peculiar to the condenser, the condenser is required to be of large capacitance. For this reason, the above multilayer ceramic condenser caught attention. In the multilayer ceramic condenser, barium titanate BaTiO.sub.3, strontium titanate SrTiO.sub.3, calcium titanate CaTiO.sub.3 and so on are employed as ferroelectric material. In this case, in order to make the thickness of the multilayer ceramic condenser thin and uniform, it is requested to make the above material ultra-fine powders. In addition, in this multilayer ceramic condenser, lead is mixed into its material in view of firing property and temperature characteristic. If the firing temperature is high, the lead is partly evaporated so that the multilayer ceramic condenser of uniform characteristic can not be provided. If the ultra-fine powder of the metal titanate such as barium titanate BaTiO.sub.3 or the like is finer, the firing temperature can be suppressed lower, so that also in this point, these metal titanates are required to be ultra-fine powder.
Moreover, the metal titanate ultra-fine powder such as barium titanate BaTiO.sub.3, strontium titanate SrTiO.sub.3, calcium titanate CaTiO.sub.3 ultra-fine powder and so on is desired as electrostrictive material and piezoelectric material for the purpose of improving the characteristics thereof. Further, the metal titanate ultra-fine powder is demanded as transparent ceramics. Because, as described above, if the particle size is fine and uniform, it is expected that the firing temperature can be lowered.
By the way, barium titanate BaTiO.sub.3, strontium titanate SrTiO.sub.3, calcium titanate CaTiO.sub.3 or the like has been manufactured by calcination. More particularly, barium carbonate BaCO.sub.3 powder and titanium oxide powder are mixed and calcined at 1000.degree. to 1200.degree. C. Or strontium carbonate SrCO.sub.3 powder and titanium oxide powder are mixed and calcined at 1000.degree. to 1300.degree. C. to cause calcination or calcium carbonate CaCO.sub.3 powder and titanium oxide powders are mixed and calcined at 1000.degree. to 1200.degree. C. to cause calcination. The calcined material thus made is mechanically ground to be fine powder. Thus, the particle size was significantly large and was not uniform. Accordingly, in order to obtain the fine and uniform particle, it is necessary to perform the sieving to eliminate large particle.
On the other hand, recently, it has been proposed to synthesize the metal titanate fine particle such as barium titanate BaTi0.sub.3 and strontium titanate SrTiO.sub.3, by employing metal alkoxide. This previously proposed method, however, results in high manufacturing cost and therefore is not carried out in practice. The size of BaTiO.sub.3 particle manufactured by this method is 500 .ANG..
The crystal system of barium titanate BaTiO.sub.3 obtained according to the above calcination method was tetragonal system (a.sub.0 =3.994 .ANG. and c.sub.0 =4.038 .ANG.), and the crystal system of the product produced by the alkoxide method was cubic.